Pepcid^® (famotidine) is commonly used to treat conditions affecting the esophagus, stomach, and intestines (including GERD, heartburn, and ulcers). The drug is available in both prescription and over-the-counter forms. It can be taken once or twice a day, or as needed. Pepcid blocks the action of a specific histamine receptor in the stomach, which reduces the amount of acid produced. Pepcid side effects can include diarrhea, constipation, and dizziness. Among the conditions that you should let your healthcare provider know about before you take Pepcid are kidney problems and any allergies you may have (including allergies to foods, dyes, or preservatives). A few alternatives to Pepcid include other H2 blockers, antacids or foaming agents, and proton pump inhibitors (PPIs).